Resource diversity disturbs marine Vibrio diversity and community stability, but loss of Vibrio diversity enhances community stability

Abstract Vibrio is a salt‐tolerant heterotrophic bacterium that occupies an important ecological niche in marine environments. However, little is known about the contribution of resource diversity to the marine Vibrio diversity and community stability. In this study, we investigated the association among resource diversity, taxonomic diversity, phylogenetic diversity, and community stability of marine Vibrio in the Beibu Gulf. V. campbellii and V. hangzhouensis were the dominant groups in seawater and sediments, respectively, in the Beibu Gulf. Higher alpha diversity was observed in the sediments than in the seawater. Marine Vibrio community assembly was dominated by deterministic processes. Pearson's correlation analysis showed that nitrite (NO2−‐N), dissolved inorganic nitrogen (DIN), ammonium (NH4+‐N), and pH were the main factors affecting marine Vibrio community stability in the surface, middle, and bottom layers of seawater and sediment, respectively. Partial least‐squares path models (PLS‐PM) demonstrated that resource diversity, water properties, nutrients, and geographical distance had important impacts on phylogenetic and taxonomic diversity. Regression analysis revealed that the impact of resource diversity on marine Vibrio diversity and community stability varied across different habitats, but loss of Vibrio diversity increases community stability. Overall, this study provided insights into the mechanisms underlying the maintenance of Vibrio diversity and community stability in marine environments.


| INTRODUC TI ON
Clarifying the association between diversity and community stability is a core issues in ecology (Donohue et al., 2013).The term biodiversity includes taxonomic and phylogenetic diversity (Cadotte et al., 2012;Vellend, 2003).Taxonomic diversity refers to the richness and abundance of species (Craven et al., 2018), whereas phylogenetic diversity describes the diversity of evolutionary lineages (Cadotte et al., 2012).Community stability is defined as the capacity to withstand environmental disturbances (Shade et al., 2012(Shade et al., , 2013)).
For example, Jiao et al. (2019) suggested that, as alpha diversity increases, bacterial communities become more stable in terrestrial ecosystems.In contrast, Yang et al. (2023) revealed that the loss of microbial diversity enhances community stability in soil ecosystems.
These studies demonstrate that the relationship between biodiversity and community stability is complex and varies in heterogeneous habitats.
Heterotrophic bacteria are prevalent in the marine ecosystem and exhibit high taxonomic and phylogenetic diversity (Hou et al., 2015;Torsvik et al., 2002).Vibrio, a typical heterotrophic bacterium with salt tolerance that is widely distributed in marine environments, plays a crucial role in marine food webs and nutrient cycling (Farmer et al., 2015;Moriarty, 1998;Thompson, Iida, & Swings, 2004;Westrich, 2015).Vibrio species, such as V. cholerae, V. parahaemolyticus, and V. vulnificus, can be pathogenic to aquatic animals and humans via the consumption of contaminated seafood (Chiang & Chuang, 2003;Colwell & Spira, 1992;Guin et al., 2019).
Marine Vibrio taxonomic and phylogenetic diversity studies have recently received increased attention (Kopprio et al., 2020;Vezzulli et al., 2009;Xu et al., 2021).For example, Chen et al. (2020) reported that there were significant differences in marine Vibrio diversity across different seasons in the Beibu Gulf.Wang et al. (2019) discovered significant differences in taxonomic diversity among various sea areas.Environmental factors (e.g., water properties and nutrients) can regulate the marine Vibrio diversity (Chen et al., 2020;Siboni et al., 2016;Urdaci et al., 1988;Xu et al., 2021).Takemura et al. (2014) conducted a meta-analysis and found that dissolved organic carbon (DOC) has a strong impact on the marine Vibrio community.Xu et al. (2020) observed that the marine Vibrio taxonomic diversity is driven by temperature, dissolved oxygen (DO), nitrate (NO − 3 -N), and nitrite (NO − 2 -N) in Dongshan Bay.Li et al. (2020) identified ammonium (NH + 4 -N) and dissolved inorganic phosphorus (DIP) as key factors affecting the community structure of marine Vibrio in eutrophic and oligotrophic groups in the Beibu Gulf, respectively.
The ecological evolutionary and biogeographical that affect the maintaining mechanism of marine microorganisms are highly complex (Sichert & Cordero, 2021), and the biodiversity and community stability of various habitats are sustained by multiple factors (Sichert & Cordero, 2021).Despite advancements in our understanding of marine Vibrio diversity, the relationship between diversity and community stability and its response to changes in the ecological niche remains unclear.
Community assembly not only affects diversity but also indirectly affects community stability (Chase et al., 2011).Microbial community assembly is simultaneously influenced by stochastic and deterministic processes (Zhou & Ning, 2017).Deterministic processes emphasise the abiotic environment (i.e.environmental filtration) and biotic interactions within communities (Zhou & Ning, 2017).In contrast, stochastic processes emphasise unpredictable events such as birth, death, dispersal, and colonisation (Li et al., 2020).The distribution of marine Vibrio is influenced by both deterministic and stochastic processes (Jesser Kelsey et al., 2018).Li et al. (2020) demonstrated that the most important process for the assembly of the marine free-living Vibrio community in the Beibu Gulf is stochastic process.Currently, there is a lack of information regarding how community assembly affects Vibrio diversity and community stability in marine habitats.
The Beibu Gulf is a semi-enclosed bay located in the northwest of the South China Sea, and a large number of estuaries and frequent human activities have resulted in abundant nutritional resources, which resulting in imbalanced environmental characteristics and an uneven distribution of resources (Chen et al., 2009;Lai et al., 2014).
To explore the relationship among the resource diversity, taxonomic diversity, phylogenetic diversity, and community stability of marine Vibrio, we analysed samples from different layers of seawater and sediment from the Beibu Gulf using high-throughput sequencing of the Vibrio-specific 16S rRNA gene (Liang et al., 2019;Siboni et al., 2016) and aimed to reveal the (i) community structure and assembly process of marine Vibrio in different habitats, (ii) influence of resource diversity on taxonomic and phylogenetic diversity, and (iii) key drivers affecting the relationship between marine Vibrio diversity and community stability in different habitats.We hypothesised that resource diversity influences the taxonomic and phylogenetic mechanisms underlying the maintenance of Vibrio diversity and community stability in marine environments.

K E Y W O R D S
16S rRNA gene, assembly process, community stability, resource diversity, Vibrio

| Sampling sites and environmental parameters
The sampling sites were located in the Beibu Gulf near Guangxi Province (Figure S1).In total, 405 samples from 25 sites were collected from seawater at various depths and sediments during open cruises of the Beibu Gulf on 10 August 2021.Seawater was sampled from each site at two to three depths ranging from 3 to 40 m, and the sediment samples were divided into four categories: the surface layer of seawater (SS), the middle layer of seawater (MS), the bottom layer of seawater (BS), and sediment (SE) (Figure S1).
The SS, MS, BS, and SE groups comprised 125, 85, 110, and 85 samples, respectively.At each site, five replicate water samples were collected using a 5-L sterile bucket.All seawater samples were stored at 4°C before Vibrio isolation and the analysis of environmental factors.Sediment replicates were collected from each site using a 0.05-m 2 van Veen grab and pooled together before treat-

| DNA extraction and PCR amplification
Genomic DNA of seawater extraction was performed by a DNeasy PowerWater Kit (QIAGEN, USA) and 0.22μm pore size polycarbonate membranes according to the manufacturer's protocols.Sediment DNA was extracted from each sediment sample (0.5 g) using PowerSoil DNA Isolation Kits (Mo Bio Laboratories, Inc., Carlsbad, CA, USA).DNA yield and purity were evaluated using a Nanodrop-2000 Spectrophotometer (Thermo Scientific, USA).The DNA sample was preserved at −80°C.The regions of the Vibrio-specific 16S rDNA were amplified using primers 169F (5′-GGCGTAAAGCGCATGCAGGT-3′) and 680R (5′-GAAATTCTACCCCCCTCTACAG-3′) (Thompson, Randa, et al., 2004).A total reaction volume of 20 μL of PCR mixture containing 2 μL of DNA template, 6 μL of ddH 2 O, 10 μL of 2 × Taq PCR Mastermix (TianGen, China), and 2 μL of forward and reverse primers was used.Using a Bio-Rad thermocycler (Hercules, CA, USA), the amplification process was as follows: an initial activation step at 94°C for 1 min, followed by 35 cycles of denaturation at 95°C for 30 s, annealing at 56°C for 30 s, and extension at 72°C for 30 s, and a final elongation step at 72°C for 10 min.Ultrapure water was used as a negative control instead of the sample solution to rule out the possibility of false-positive PCR results.PCR products were verified using 2% agarose gel electrophoresis and visualised using a UV light and gel imaging system.

| High-throughput sequencing
A purified library was prepared according to Illumina library preparation protocols and transferred to an Illumina MiSeq platform for sequencing at Majorbio Co. Ltd. (Shanghai, China).Sequences with low-quality reads were removed using the DADA2 denoising method in Qiime2 (Caporaso et al., 2010).The amplicon sequence variants (ASVs) from Illumina scale amplicon data without arbitrary dissimilarity thresholds were used for subsequent analyses (Callahan et al., 2017).Taxonomic classification of ASVs was completed using a local BLASTN (cut-off E-value 1e-10) against the Ribosomal Database Project (RDP) database (Release 11) (Cole et al., 2013).
All sequence data were deposited in GenBank under BioProject Accession.PRJNA1029771.

| Calculation of community stability
Vibrio community stability was evaluated using the average variation degree (AVD), which was calculated using the degree of deviation from the mean of the normally distributed ASV relative abundance (Xun et al., 2021).Firstly, the degree of variation for each ASV was calculated using the following equation: where a i is the variation degree for an ASV, x i is the rarefied abundance of the ASV in one sample, x i is the average rarefied abundance of the ASV in one sample group, and δ i is the standard deviation of the rarefied abundances of the ASV in one sample group.Secondly, the AVD was calculated using the following equation: where k is the number of samples in one sample group and n is the number of ASVs in each sample group.

| Calculation of resource diversity
The resource diversity (RD) index was used to represent multidimensional resources in different habitats based on Liu et al. (2020).We chose TOC, total nitrogen (TN), and total phosphorus (TP), which represent the carbon, nitrogen, and phosphorus resources, respectively, to compute RD.We used the polygon radar chart method modified and improved by Hongliang et al. (2008) to calculate the differences in resources.The circumferential angle of each index varies with the total number of indices and index weight changes.
The area (S) and perimeter (L) were expressed as: where n represents the number of indexes, f j represents the weight of the jth index (each index was assigned the same weight in this study), and r max , r min , and r j represent the maximum and minimum radii and radius of the jth index, respectively.Next, v i1 and v i2 were standardised to represent resource richness and evenness, respectively: Based on v i1 and v i2 , the RD index was calculated using the following:

| Calculation of phylogenetic diversity
We used phylogenetic species variability (PSV), phylogenetic species richness (PSR), and phylogenetic species evenness (PSE) to measure the phylogenetic diversity of the marine Vibrio community.The PSV measures the degree of phylogenetic relatedness of Vibrio species within a community (Guevara Andino et al., 2017) and was calculated using the following equation: The n represents the number of species and C represents a covariance matrix, and trC is the sum of the diagonal elements of C, ∑ C indicates the sum of all elements in C.
PSR considers species richness and relatedness (Guevara Andino et al., 2017): PSE simultaneously considers the phylogenetic information and species evenness (Guevara Andino et al., 2017): The PSE is derived from a community with a phylogeny given by C to a community with evolutionarily independent species with equal species abundances (m i = m i ), where m is the total number of individuals and m i is the number of individuals of species i. M is an n × 1 column vector containing values of m i and diag gives an n × 1 column vector of the main diagonal of C. M′ is the transition of M.

| Statistical analysis
We calculated the Richness, Shannon, Simpson, and Chao1 (Good, 1953;Kemp & Aller, 2004) indices, and using the Shannon index to represent the alpha diversity and Richness index to represent e the gamma diversity.We used the vegan package in R as follows: visualise the Bray Curtis dissimilarity of Vibrio communities using nonmetric multidimensional scaling (NMDS), and determine significant differences between communities through similarity analysis (ANOSIM).The impact of environmental factors on Vibrio communities was measured using the Mantel test.
Correlations were calculated using the Spearman's rank method.
Use R package "ggplot2" for linear regression analysis.Use the "plspm" package for partial least squares path model (PLS-PM) analysis.As mentioned earlier, null model analysis was performed to classify the community assembly process (Stegen et al., 2013).
Based on phylogenetic and taxonomic characteristics, the beta diversity metrics using the β-nearest taxon index (βNTI) and Bray-Curtis-based Raup-Crick were generated for the evaluation of community assembly.

| Composition and diversity of marine Vibrio
In total, 167,615 high-quality sequences were obtained from all samples.The average number of detected sequences was 34,857 ± 1743 and the average ASV of each sample was 1252 ± 72.Good's coverage values were 98.07 ± 0.97, indicating that the vast majority of the Vibrio community was recovered.V. campbellii was the most abundant species in seawater, including SS, MS, BS samples (52.94%, 60.59%, 52.21%, respectively), followed by V. carbbeanicus (7.75%, 5.90%, 4.29%, respectively).V. hangzhouensis (27.91%) and V. campbellii (6.43%) were the most abundant species in SE samples (Figure 1).Besides, among the dominant Vibrio species, some common pathogenic strains, such as V. parahaemolyticus, V. campbellii, and V. alginolyticus, were detected in different layers of seawater and sediment samples.Notably, the proportions of V. ishigakensis and V. azureus increased vertically along the depth gradient from SS to SE.
In contrast, the relative abundances of V. diabolicus and V. caribbeanicus gradually decreased (Figure 1).
In this study, the Shannon and Richness indices were used to assess marine Vibrio alpha and gamma diversity, respectively.Alpha and gamma diversity were the highest in the SE group in comparison to the three other habitats groups, whereas the lowest alpha diversity observed in the MS group (Figure 2a-d).The NMDS plot based on the Bray-Curtis distance revealed the variation between the marine Vibrio communities from all four habitats (Figure 2e).for 24.10%, 18.46%, and 29.71%, respectively.The importance of homogeneous selection (HoS) was higher in SE samples (3.40%) than in ED samples (2.35%) (Figure 3).In general, deterministic processes made a more important contribution to the dynamics of marine Vibrio communities in different habitats, especially in SE, than stochastic processes.

| Contribution of resource diversity to marine Vibrio diversity and community stability
We explored the linear correlation between RD and taxonomic diversity.Alpha, beta, and gamma diversities were significantly positively correlated with RD in the MS and BS samples (p < .05)(Figure 4).In the SS samples, RD was significantly correlated with beta diversity (r 2 = .03,p < .001)and significantly negatively correlated with gamma diversity (r 2 = .04,p = .012)(Figure 4).Only beta diversity was significantly and positively correlated with RD in the sediment samples (r 2 = .03,p < .001)(Figure 4).For the impact of RD on and phylogenetic diversity, we found that the PSV, PSR, and PSE were significantly positively correlated with RD in the MS samples (p < .01),whereas the opposite trend was observed in the BS samples (Figure 5).In the SS samples, there was a significant positive correlation (r 2 = .05,p = .008)between PSR and RD and PSV, whereas only PSE was significantly negatively correlated with RD in the SE samples (r 2 = .13,p = .001)(Figure 5).Furthermore, we analysed the correlation between AVD and RD.In the SS and SE samples, AVD significantly decreased (p < .05)with increasing RD (Figure 6).
Conversely, AVD was significantly and positively (p < .05)correlated with RD in BS and MS samples (Figure 6).Collectively, these results suggest that an increase in resource diversity has different effects on marine Vibrio diversity and community stability in different habitats.
Linear regression analysis was used to investigate the correlation between the marine Vibrio diversity and community stability.
In terms of the taxonomic diversity, AVD was significantly positively correlated with alpha, beta, and gamma diversity in all four habitats (p < .01)(Figure 7).The relationship between alpha diversity and AVD was strongest in SE samples (r 2 = .55,p < .001),whereas the beta diversity of BS samples had a stronger linear correlation with AVD than the other samples (r 2 = .13,p < .001),and gamma diversity showed the strongest positive correlation with AVD in the MS samples (Figure 7).Furthermore, Pearson's correlation analysis showed that in all habitats, beta and gamma diversities were significantly positively (p < .05)correlated with AVD (Table S1).
Our results showed that increased taxonomic diversity weakened Vibrio community stability in different habitats.Moreover, for the phylogenetic diversity, the linear regression analysis demonstrated that PSV was positively correlated with AVD in the SS, MS, and SE samples (p < .01)(Figure 8).PSR was positively correlations with the AVD in all groups, and PSE was significantly positively correlated with AVD in the MS and BS samples (p < .001),but no significant correlation was observed in the SS and SE samples (p > .05)(Figure 8).
Supplementally, Pearson's correlation analysis showed consistent results with the linear regression analysis, with significant positive correlations between AVD and PSV, PSE, and PSR in all groups (Table S1).These results suggest that, in all habitats, an increase in phylogenetic diversity leads to a decrease in the stability of the marine Vibrio community.
Collectively, these observations suggested that nutrients are important for the diversity and community stability of marine Vibrio.
Linear regression analysis was used to determine the potential impact of geographical distance on the taxonomic and phylogenetic diversity of marine Vibrio.Beta and gamma diversity significantly increased with increasing geographic distance (p < .05)(Figure S3).Alpha diversity was significantly positively correlated with geographic distance (p < .001) in the SS and SE samples, whereas a significant negative correlation was observed in the BS samples (r 2 < .01,p < .001),and there was no significant correlation in the MS samples (p > .05)(Figure S3).PSV, PSV, and PSR were significantly positively correlated with geographic distance in the SS and SE samples (p < .001).In the MS samples, PSV and PSR were significantly positively correlated with geographic distance (p < .001),whereas there was no significant correlation with PSE (p > .05)(Figure S4).Geographical distance was significantly positively correlated with PSR (r 2 < .01,p = .026)but significantly negatively correlated with PSE (r 2 < .01,p < .001),and there was no significant correlation with PSV (p > .05) in the BS samples (Figure S4).PLS-PM was constructed to analyse the relationship between AVD and taxonomic and phylogenetic diversity, as well as nutrients, water properties, RD, and spatial diversity, in different habitats.
Nutrients had a significant positive (p < .001)effect on alpha diversity (Figure 9a).Water properties had the strongest and most significant (p < .001)effects on beta and gamma diversity in the SS samples (Figure 9a), and RD was identified as the most important factor influencing phylogenetic diversity (p < .001)(Figure 9a).In the case of MS samples, nutrients had the strongest significant (p < .001)effect on alpha and beta diversity (Figure 9d), C (COD and TOC) was the main F I G U R E 5 Linear regressions for phylogenetic diversity (PSE, PSR and PSV), associated with RD.
contributing factor to nutrients (Figure 9c,f).Spatial variation and RD were the strongest factors that significantly (p < .001)influenced gamma diversity and phylogenetic diversity, respectively (Figure 9d).
For the BS samples, spatial variation mainly affected alpha and beta diversity, and RD mainly affected gamma and phylogenetic diversity (p < .001)(Figure 9g).Additionally, in SE samples, water properties had the most significant effect on alpha and gamma diversity, whereas spatial variation had the strongest effects on beta and phylogenetic diversity (p < .001)(Figure 9j).Furthermore, PLS-PM revealed that taxonomic and phylogenetic diversity jointly regulated marine Vibrio community stability.Specifically, gamma diversity had the strongest positive (p < .001)effect on AVD in the SS, MS, and BS samples (Figure 9a,g,j).Phylogenetic diversity mainly affected AVD in the SE samples (p < .001).Spatial variation had the strongest potential impact on AVD in the MS and SE groups (Figure 9e,k).RD had an indirect negative effect on AVD in the SS group (Figure 9b) and nutrients had the strongest indirect effect (Figure 9h).Overall, water properties, nutrients, RD, and spatial variation had the greatest effects on diversity.RD was the most important factor for phylogenetic diversity in all three seawater layers.The stability of the marine Vibrio community is regulated by taxonomic and phylogenetic diversity.

| DISCUSS ION
Vibrio occupies an important ecological niche in marine environments (Heidelberg et al., 2002;Zhou et al., 2021).Most studies on marine Vibrio ecology have focused on pathogenic groups or revealed their diversity and key environmental drivers in specific habitats (Amin et al., 2016;Jesser Kelsey et al., 2018;Mansergh & Zehr, 2014;Matteucci et al., 2015;Thompson, Randa, et al., 2004).However, environmental resources often exhibit enormous complexity, thus, quantifying multidimensional resource components can better elucidate the response mechanisms of marine Vibrio to environmental changes.To date, little is known about the effects of resource diversity on marine Vibrio diversity and community stability.In this study, we investigated the contribution of resource diversity to taxonomic and phylogenetic diversity, as well as community stability, in various habitats.
Our results showed that resource diversity affects marine Vibrio diversity and community stability.Specifically, the influence of resource diversity on marine Vibrio community stability and diversity across distinct habitats, but the increase in taxonomic and phylogenetic diversity led to a reduction in the community stability of marine Vibrio.

F I G U R E 6
Linear regressions for RD associated with AVD in different habitats.

| Taxonomic and phylogenetic diversity of marine Vibrio varies in seawater and sediment samples
In recent years, many studies have been conducted on pathogenic Vibrio species that affect human and fishery health, especially in marginal seas severely affected by anthropogenic activities (Di et al., 2017;Froelich et al., 2017;Liang et al., 2019;Pruzzo et al., 2005;Vezzulli et al., 2009).For example, Di et al. (2017) found that V. parahaemolyticus and V. alginolyticus are ubiquitous in tidal water and mud year-round along the southern coast of South Korea.Liang et al. (2019) reported that V. campbellii is dominant in the South Yellow Sea during summer.These findings suggest that the distribution of pathogenic Vibrio in marine environments is related to the impact of available resources derived from human activities such as aquaculture and pollution emissions.In our study, we identified three common pathogenic strains: V. parahaemolyticus, V. campbellii, and V. alginolyticus.The distribution of V. parahaemolyticus and V. alginolyticus in sediment and seawater was significantly lower than that of V. campbellii.Notedly, our results indicate that V. hangzhouensis is most abundant in the sediment of the Beibu Gulf, whereas V. campbellii exhibited the highest relative abundance in all three seawater habitats (Figure 1).We speculate that this phenomenon may be explained by the influence of the special habitat in the Beibu Gulf, which has led these species to exhibit diverse.
As expected, our findings suggest that both alpha and gamma diversity were highest in the sediment samples (Figure 2a-d).
Similarly, (Wang et al., 2019;Wang, Liu, et al., 2022) found that in the marginal seas of China (including the Yellow Sea, East China Sea, and South China Sea), the diversity of marine Vibrio in sediments is generally higher than that in seawater.These findings corroborate previous evidence that sediments serve as a highly favourable ecological niche for marine Vibrio (Aravindraja et al., 2013;Vezzulli et al., 2009).Additionally, there is evidence that an increase in nutrient concentrations promotes an increase in marine Vibrio diversity (Li et al., 2020).Sediments harbour higher organic matter content than seawater (Hedges & Keil, 1995;Riley & Chester, 2013), which may result in the highest diversity of marine Vibrio observed in the sediment.The NMDS results illustrated F I G U R E 7 Linear regressions for AVD associated with marine Vibrio alpha diversity, beta diversity, and gamma diversity.p-Values indicate significant differences.that the marine Vibrio structure within the sediment exhibited a more pronounced divergence than that in other habitats.In contrast, the three seawater habitat samples partially overlapped (Figure 2e).This can be attributed to the distinct characteristics of seawater and sediment.Aquatic systems exhibit fluidity and interconnectedness (Chen et al., 2019;Zeng et al., 2019), and the continual vertical exchange of seawater amplifies the potential for taxonomic interchange among habitats.In contrast, sediments evolve over time through gradual accumulation, creating distinctive and stable conditions that facilitate the proliferation of marine Vibrio.Consequently, the discernible distinctions between seawater and sediment habitats are not surprising.The Vibrio is highly diverse genetically (Travers et al., 2015).
Here, we employed PSV, PSR, and PSE as comprehensive indicators to assess the phylogenetic diversity of marine Vibrio.The PSV primarily quantifies the degree to which species are phylogenetically related within a community.Compared to PSV, PSR incorporates species richness and phylogenetic information, whereas PSE integrates relative abundance while considering phylogenetic information and species consistency (Helmus et al., 2007).Our results demonstrated that PSE and PSR exhibited the highest values in the sediment samples, indicating that marine Vibrio species harbour greater species richness and more uniform distribution across phylogenetic branches in the sediment.This result can be attributed to the relatively stable environmental conditions in the sediment (Aller, 1994) which offer favourable conditions for the reproduction and survival of diverse marine Vibrio species, fostering their more equitable distribution across various phylogenetic lineages.Conversely, the highest degree of PSV was observed in the middle layer of seawater, suggesting that marine F I G U R E 8 Linear regressions for phylogenetic diversity (PSE, PSR, and PSV) associated with AVD.

F I G U R E 9
Path analysis representing the relationship among average variation degree, alpha diversity, beta diversity, gamma diversity, phylogenetic diversity, nutrients, resource diversity, spatial, and water properties in the subtropical sea.The red arrow represents a negative correlation, which means that an increase in the variation of the factors will reduce the diversity, and the blue arrow represents a positive correlation, which means that an increase in the variation of the factors will promote the diversity.The number is the r value; the asterisk indicates the p value: *p < .05;**p < .01;***p < .001,and Vibrio.
Vibrio populations in this habitat manifested higher variability in their phylogenetic development.The middle layer of seawater is exchanged with both the surface and bottom layers, resulting in stronger fluctuations in its physicochemical characteristics and complex conditions, potentially introducing a more complex and diverse environmental species pool.Consequently, these populations may experience greater selection pressure and adaptation requirements, leading to enhanced differentiation and diversity in their phylogenetic development.Pontarp et al. (2012) showed that habitat filtration shapes marine bacterial communities on a global scale.Pearson's correlation analysis revealed a strong correlation between marine Vibrio communities and various environmental factors in different habitats (Table S1).Therefore, we speculate that deterministic processes dominate the assembly process of marine Vibrio community.In this study, we used a null modelling-based framework to detect the assembly process of the marine Vibrio community and revealed that deterministic processes were the main forces promoting the turnover of the marine Vibrio community in all four habitats, where heterogeneous selection was the predominant process.Heterogeneous selection is a deterministic concept that refers to different environmental selective forces that may drive a community towards greater dissimilarity (Dini-Andreote et al., 2015;Vellend, 2010).The heterogeneous selection of the Vibrio community can be attributed to heterogeneous environmental factors that impose strong selective pressures (Li et al., 2021).Our research showed that βNTI was significantly correlated with most environmental factors, such as temperature, salinity, DIN, and DIP.Previous research has shown that abiotic factors such as temperature and nutrients are significantly related to the marine Vibrio community (Siboni et al., 2016;Takemura et al., 2014;Wright et al., 1996;Zhang et al., 2018).These factors have been proven to drive highly deterministic processes in various ecosystems (Guo et al., 2014;Lawrence & William, 2001;Zakem et al., 2018).Notably, our findings demonstrated the impact of stochastic processes mediated by ecological drift on Vibrio community in the surface, middle, and bottom layers of seawater.This effect stems from several causes.Firstly, certain Vibrio species perform similar functions, resulting in functional redundancy and niche overlap (Zhou & Ning, 2017), thereby increasing their potential for ecological drift.Secondly, the connectivity and mobility of seawater play a crucial role in promoting ecological drift (Chen et al., 2019;Zeng et al., 2019).Interestingly, our findings contradict a previous report of similar investigations in the Beibu gulf (Li et al., 2020).The reason for this contradiction may be attributed to the study of spatial scale differences.Shi et al. (2018) reported that deterministic patterns are more likely to be displayed on a large scale, whereas stochasticity tends to dominate on a local scale.Additionally, stochastic processes are more influential when there are few environmental variations or selection pressures (Shi et al., 2018).In this study, we sampled a wider range of spaces and diverse habitats, representing greater environmental differences and selection pressures.Consequently, deterministic processes dominated the construction of the marine Vibrio community.Furthermore, the regression analysis results revealed a significant positive correlation between marine Vibrio diversity and geographical distance (Figures S2 and S3), providing additional support for our conclusions.

| Loss of taxonomic and phylogenetic diversity enhance community stability
The relationship between biodiversity and community stability has long been controversial in ecology (Hu et al., 2022;Huelsmann & Ackermann, 2022;Tilman et al., 2006).Owing to the intricate taxonomic and genetic diversity of microbial communities, characterising their interactions remains extremely challenging (Alivisatos et al., 2015).The prevailing consensus suggests that higher diversity contributes to enhanced community stability (Ives & Carpenter, 2007).However, contrasting views suggest that a higher microbial diversity may diminish community stability.For instance, Lehman and Tilman (Lehman & Tilman, 2000) researched a multi-species competition model and their results showed that increase of biodiversity weakens community stability.Fischer et al. (2016) reported that increased gamma diversity results in decreased community stability.In our study, we observed a significant positive correlation between the average degree of variation and taxonomic and phylogenetic diversity, implying that a reduction in marine Vibrio diversity corresponds to an increase in community stability (Figures 7 and 8).Supplementally, Pearson's correlation analysis revealed that, in all habitats, beta and gamma diversity, as well as PSV, PSE, and PSR, were significantly positively (p < .05)correlated with AVD (Table S1).Previous studies have demonstrated that interaction strength is crucial for stability (Yodzis, 1981), and competition for resources among species may result in diminished community stability (Huelsmann & Ackermann, 2022).In general, the proportion of potential competitors participating in interspecific interference varies, and their interactions typically produce unstable effects (Yodzis, 1981).
Additionally, the "hunger games" hypothesis suggests that cooperative interactions (e.g., cross-feeding) are prevalent in bacterial communities, and a nutrient-rich environment intensifies competition among species (Dai et al., 2022).Previous studies have demonstrated that marine Vibrio exhibit diverse metabolic abilities, including nitrogen fixation, phosphorus compound absorption, organic matter utilisation, and remineralisation (Thompson, Iida, & Swings, 2004;Zhang et al., 2018).By employing these distinct species can exploit specific nutrient resources more efficiently, thereby gaining advantages in particular habitats.Overall, competition for nutrition among Vibrio species may result in stronger negative interactions, ultimately leading to a decrease in the community stability of marine Vibrio.

| Resource diversity significantly affects marine Vibrio diversity and community stability
Previous studies have established that environmental factors exert a significant influence on marine Vibrio (Amin et al., 2016;Liang et al., 2019;Takemura et al., 2014).However, most of these investigations have been constrained to elucidating the individual contributions of distinct factors.In this study, we observed a substantial correlation between environmental factors and marine Vibrio.It is well known that the interplay between microbial communities and the environment is often intricate.Therefore, exclusive emphasis on the contribution of a single factor may not be sufficient to comprehensively unravel the intricate relationship between resources and the marine Vibrio community (Wang, Du, et al., 2022).
To comprehensively quantify multidimensional resources, we employed the RD index, which considers both the average abundance of resources and their balance (Wang, Du, et al., 2022), to evaluate resource diversity across various marine habitats, and revealed its impact on the diversity and community stability of marine Vibrio.
PLS-PM showed that the effects of RD on alpha, beta, and gamma diversity exhibited heterogeneous patterns across the four studied habitats (Figures 8 and 9a,d,g,j).Specifically, RD had a negative effect on alpha diversity only in the middle layer of seawater (Figure 9d), whereas it had a positive effect in other habitats.Furthermore, RD was positively correlated with beta diversity in the surface and middle layers of seawater (Figure 9a,d).However, no significant correlation emerged between RD and gamma diversity, except in the middle seawater layer (Figure 9d).These findings underscore the intricate relationship between diversity metrics and resource diversity, revealing inherent inconsistency (Muscarella et al., 2019).At the vertical level, these inconsistencies may have been caused by habitat differences.
Temperature and salinity are the most common key factors affecting marine Vibrio, whereas other parameters vary according to the habitat.Geographical distance may be another pivotal factor.Previous studies have shown that marine Vibrio in seawater and sediments are related to geographical distance (Wang et al., 2019;Wang, Liu, et al., 2022).Our results showed that alpha, beta, and gamma diversities were significantly correlated with geographic distance in almost all habitats (Figure S3).These differences may be attributed to variations in competitive ability (Leibold, 1999) and shared limitations across species (Stevens & Carson, 2002).It is worth noting that RD exerted a positive effect on phylogenetic diversity in all four habitats (Figure 9a,d,g,j).Theoretically, resource enrichment can foster increased diversity, thereby supporting more intricate microbial communities (Smith, 2007;Worm et al., 2002) and, ultimately, promoting gene flow and maintaining genetic diversity within species (Beger et al., 2014;Fu et al., 2016).Moreover, when resources in the ecosystem are abundant and diverse, species may be more likely to cope with environmental pressures, reducing the risk of individual genetic damage and maintaining phylogenetic diversity.
Regression analysis showed that RD and AVD exhibited different patterns in different habitats, with a negative correlation in the surface layer of seawater and sediment and a positive correlation in the middle and bottom layers.This indicates that an increase in resource diversity in the surface water and sediments enhances the marine Vibrio community stability.However, the opposite trend was observed in the middle and bottom layers.Additionally, PLS-PM indicated that RD indirectly affects community stability through diversity.Previous studies have shown that there are usually more biologically available resources (such as light energy and organic carbon) in surface water and sediment (Garel et al., 2019;Hedges & Keil, 1995;Riley & Chester, 2013;Skoog & Benner, 1997) and that the diversity of these resources may support the survival and reproduction of different biological species, thereby promoting community stability.Middle and bottom water resources are relatively scarce and experience greater changes in temperature and pressure (Garel et al., 2019), which may have different degrees of impact on species, leading to a decline in community stability.

| CON CLUS ION
In this study, the spatial distribution of marine Vibrio in different habitats was determined using PCR and high-throughput sequencing.V. hangzhouensis was most abundant in sediment in the Beibu Gulf, whereas V. campbellii was the dominant species in all layers of seawater.Sediments exhibited higher alpha and gamma diversity, and nutrients played a crucial role in the diversity and community stability of marine Vibrio.We further revealed that marine Vibrio Vibrio and community stability in the subtropical marginal sea.
ment.All sediments replicates were stored at 20°C on board and 80°C in the laboratory until DNA extraction.For Vibrio community analysis in seawater, a vacuum pump was used to sequentially filter 1 L of seawater per sample through 3μm filters (Port Washington, NY, USA) to remove debris and larger organisms, and the resulting samples were collected on 0.22μm pore size polycarbonate membranes (Millipore Corporation, Billerica, MA, USA).The environmental parameters of the samples were analysed.A portable metre (556 MPS; YSI, USA) was used to determine the temperature, salinity, pH, and DO.And the concentrations of phosphate (PO 3− 4 -P), NO − 2 -N, NO − 3 -N, and NH + 4 -N were measured by continuous flow analyser (Seal-AA3, Germany).Referring to previous methods for determining the chlorophyll a (Chl-a) (American Public Health Association, 1926).Use the TOC-VCPH analyser (Shimadzu, Japan) to determine the amount of total organic carbon (TOC).The chemical oxygen demand (COD) was measured using the alkaline KMnO4 method.DIN was indicated by the sum of NO − 2 -N, NO − 3 -N, and NH + 4 -N, while DIP was represented by the PO 3− 4 -P.
SE samples have greater separation from SS, MS, and BS samples.The ANOSIM (r = .317,p < .001)test demonstrated significant differences in the beta diversity of the marine Vibrio community in different habitats.Phylogenetic diversity analysis revealed variations in PSV, PSR, and PSE across the different habitats.PSE and PSR values were highest in the SE sample (Figure 2f,g), whereas the PSV value was highest in the MS sample (Figure 2h).Additionally, the PSE value was lowest in the BS sample, PSR value was lowest in the MS sample, and PSV value was lowest in the SS sample (Figure 2f-h).

3. 2 |
Assembly process of marine Vibrio community βNTI was performed to evaluate the relative importance of stochastic and deterministic processes in shaping marine Vibrio community assembly in different habitats.|βNTI| ≥ 2 and |βNTI| ≤ 2 represent dominant deterministic processes and stochastic processes in shaping the marine Vibrio community, respectively.The proportions of βNTI values between >2 or <−2 were 71.62%, 80.92%, 68.16%, and 95.57% for the marine Vibrio community in SS, MS, BS, and SE, respectively (Figure 3).Deterministic rather than stochastic processes dominated the assembly of marine Vibrio communities in different habitats.Additionally, to explore the potential effects of deterministic or stochastic factors on marine Vibrio community structure, we assigned deterministic and stochastic processes to five specific ecological processes.In different layers of seawater (SS, MS, and BS samples) and SE samples, heterogeneous selection (HeS) dominated the marine Vibrio community, accounting for 71.57%, 73.56%, 65.96%, and 90.33%, respectively (Figure 3).For the SS, MS, and BS samples, the importance of ecological drift (ED) was second only to that of HeS, accounting F I G U R E 2 Vibrio alpha diversity and beta diversity in different depth and habitats.(a-d) alpha diversity (Shannon, Simpson, Chao 1, and Richness) presented by box plots; statistically significant differences (p < .05)are indicated by different letter for each group.(e) Beta diversity was calculated based on Bray-Curtis dissimilarity index and visualised by nonmetric multidimensional scaling (NMDS), which was performed to analyse similarity variation in the Vibrio community.Box plots represent differences among different depth and habitats.(f-h) Phylogenetic diversity presented by box plots.PSE, phylogenetic species evenness; PSR, phylogenetic species richness; PSV, phylogenetic species variability.

F
Analysis of Vibrio community assembly in different depth and habitats.DL, dispersal limitation; ED, ecological drift; HD, homogenising dispersal; HeS, heterogeneous selection; HoS, homogeneous selection.

| 9 of 19 QIN
et al. p < .001)had the strongest influence on PSR, and pH (r = −.49,p < .001)had the most significant effect on PSE (Table metabolic pathways and enzymatic systems, marine Vibrio species compete for essential resources, enabling survival and reproduction in complex and dynamic environments.Highly competitive | 15 of 19 QIN et al. community assembly was dominated by deterministic processes.Moreover, marine Vibrio community stability was mainly influenced by NO − 2 -N, DIN, and NH + 4 -N in seawater, whereas pH was the main factor in sediment.Resource diversity, water properties, nutrients, and geographical distance had significant effects on marine Vibrio diversity and community stability.Overall, our results show that the influence of resource diversity on marine Vibrio diversity and community stability varies with habitat, however, the loss of taxonomic and phylogenetic diversity simultaneously enhanced community stability.These findings contribute to the understanding of the contribution of resource diversity to heterotrophic bacterial diversity and community stability.AUTH O R CO NTR I B UTI O N S Xinyi Qin: Conceptualization (equal); methodology (equal); supervision (equal); writing -review and editing (equal).Qinghua Hou: Conceptualization (equal); data curation (equal); formal analysis (equal); investigation (equal); methodology (equal); visualization (equal); writing -original draft (equal); writing -review and editing (equal).Huaxian Zhao: Writing -review and editing (equal).Pengbin